Forged article with prealloyed powder

ABSTRACT

These connecting rods are made from prealloyed manganese, sulfur, ferrous based powder. The prealloyed powder then is mixed with copper and carbon. The copper content is at higher than normal copper contents. The resulting forged connecting rods had an improvement in tensile strength and an improvement in fatigue strength.

TECHNICAL FIELD

[0001] This invention relates to forged articles made from ferrouspowder prealloyed with manganese and sulfur. More specifically, theforged articles are forged engine connecting rods.

BACKGROUND OF THE INVENTION

[0002] The connecting rod manufacturing process involves pressuremolding metal particles in a closed mold under significant pressure toproduce a green compact form of the rod. Next, the green compact isheated in a furnace sufficiently to form a sintered preform in whichmetal particles are bonded. Next, the sintered preform is hot forged tofinal rod shape which increases the rod's density and strength.

[0003] The automobile industry continues to challenge connecting rodmanufacturers to increase the fatigue strength of these articles. As aresult, higher performance materials are needed for forged connectingrods. The goal Is to engineer a powder metal blend to manufactureconnecting rods with the following characteristics: high strength; goodmachinability; reasonable cost, good weight and dimensional control. Ourresearch included materials considerations; metallurgical andmicrostructure evaluation; dimensional change measurements; tensilestrength; fatigue strength and machinability tests.

BRIEF SUMMARY OF THE INVENTION

[0004] The forged articles or connecting rods of this invention are madefrom ferrous based powder prealloyed with manganese and sulfur. Theprealloyed powder then is admixed with copper at higher than normalcopper contents. Materials considered were as follows. In a firstapproach, I thought that increasing Cu content from 2% to 3% or even 4%would improve the strength of connecting rods for the following reasons:Cu strengthens the ferrite, Cu hardens the ferrite, and Cu hinders graingrowth after forging. In a second approach I thought that usingprealloyed MnS base powder, instead of admixed MnS base powder, wouldimprove the strength of connecting rods for the following reasons:smaller inclusion (MnS) size, uniform inclusion (MnS) distribution, andhigher Mn content.

[0005] As a result, I used a commercially available prealloyedmanganese, sulfur, ferrous based powder for producing the forgedarticle. The prealloyed powder then is mixed with copper and carbon toproduce a mix comprising by weight percent: Component Weight Percentcopper (Cu) <2.0 to 5.0 carbon (C)   0.2 to 1.0 prealloyed MnS powderbalance

[0006] The resulting forged connecting rods had an improvement intensile strength and an Improvement in fatigue strength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a perspective view of a forged connecting rod.

DETAILED DESCRIPTION OF THE INVENTION

[0008] The methods for preparing the prealloyed powder may vary widely.Typically, the powder is prepared by atomization of a molten metalstream of iron, manganese and sulfur. The resulting particles usuallyhave an irregular spherical shape. To facilitate compaction, theatomized particles can be collected after solidification and subjectedto annealing at 1700° F. for about 1-½ hours, followed by grinding tobreak up particle cakes, and then passed through an 80 mesh sieve.

[0009] The prealloyed ferrous powder then is mixed with copper andgraphite at room temperature. The copper powder generally has a purityof 99%. The copper powder and carbon (graphite flake powder), however,are commercial grade materials. The copper powder is mixed in a range of2.0 to 5.0% by weight of the mixture. The graphite powder is added toyield a final carbon content in the product ranging from 0.2 to 1.0weight percent.

[0010]FIG. 1 illustrates forged connecting rod 10. Rod 10 has anelongated configuration extending along longitudinal axis A-A. Rod 10includes midportion 12; small end portion 14; and large end portion 16.Bore 18 is formed through small end portion 14 adapted to receive awrist or piston pin (not shown) as Is well known in the engine art.Aperture 20 is formed through large diameter end 16 and is adapted toreceive a journal of a crankshaft (not shown) as is well known in theengine art. Large end portion 16 has a side thrust face 22. Rod 10includes large end portion 16 having a pair of oppositely facing edgesor end surfaces 24. In the particular design of the connecting rod shownin FIG. 1, side thrust face 22 is in a raised plane with respect to theremaining side surface 26. Side thrust face 22 also includes a pair ofradially outwardly extending portions 28, 30 located to either side ofaperture 20. Portions 28, 30 extend radially outward from aperture 20and terminate at end of edges 24.

[0011]FIG. 1 also shows a pair of slits or creases 32, 34 formed in theside thrust face including extensions 28, 30. Each crease 32,34 isarranged to one side of aperture 20 and they are substantially alignedacross aperture 20. Creases 32, 34 extend inwardly from surfaces 28, 30to a considerable depth as Is evident by examination of leftward end 24and the cylindrical surface which forms the bore 20.

[0012] The manufacturing processes for making the connecting rod mayvary widely. For example, a green compact is made in the form of the rodby molding powder metal particles in a closed mold under great pressure,typically about 80,000 psi. This pressure molding causes the particlesto mechanically interlock and form a stable, relatively weak part butstrong enough for handling. Next, the green compact is heated in afurnace at temperatures higher than 2000 degrees F. for a period of timesufficient to cause the metal particles to bond. After sintering, thepreform has the same configuration as the green compact but is muchstronger.

[0013] The preform then is hot forged to achieve the shape and increasedensity and strength as required for a connecting rod. Typically, it ishot forged in a press at a pressure of about 60,000 psi and at atemperature of about 1800 degrees F.

[0014] Preferably, the mixture of this invention comprises: ComponentWeight Percent Cu 2.5 to 4.5 C 0.2 to 0.7 prealloyed MnS powder balance

[0015] More preferably, the mixture is: Component Weight Percent Cu 3.0to 4.0 C 0.4 to 0.7 prealloved MnS powder balance

[0016] The mixed powder of this invention may be used to forge articlesother than connecting rods. Other automotive uses include piston ringsand valve seats for internal combustion engines. Other parts Includeclutch races, differential gears and similar parts.

[0017] The following Examples further Illustrates the composition ofthis Invention.

EXAMPLE I

[0018] (Prior Art)

[0019] The following shows average tensile results for standardproduction powders with varying amounts of copper. Results for astandard manganese sulfur admixture (rather than the prealloyed powderof this invention) also are shown. The average is based on 6 runs.TENSILE RESULTS Commercial Grade Prealloyed Mn S Standard ProductionPowder Powder 2% Cu 3% Cu 4% Cu 2% Cu (psi) (psi) (psi) (psi) Avg.124,534 144,788 145,046 120,268 StDev 3,641 2,771 3,805 1,755

EXAMPLE II

[0020] (Prior Art)

[0021] The following shows fatigue results for standard productionpowders with varying amounts of copper. Results for a standardprealloyed manganese sulfur powder also are shown. FATIGUE RESULTSCommercial Grade Preallayed Standard production powder Mn S Powder 2% Cu3% Cu 4% Cu 2% Cu (ksi) (ksi) (ksi) (ksi) Endurance Limit @ 50% 45.2152.63 52.64 50.77 Scatter 1.07 2.18 2.10 1.88 Standard deviation (s)0.28 0.49 0.49 0.43

EXAMPLE III

[0022] Tensile Results for the prealloyed Mn S ferrous powder of thisinvention with 3% Cu show an improvement of approximately 5% in tensilestrength compared to standard production.

EXAMPLE IV

[0023] Fatigue results for the prealloyed Mn S ferrous based powders ofthis invention with 3% Cu show an improvement of 19% in fatigue strengthcompared to standard production.

[0024] In addition to these embodiments, persons skilled in the art cansee that numerous modifications and changes may be made to the aboveinvention without departing from the Intended spirit and scope thereof.

I claim:
 1. A powder useful for producing forged articles comprising amixture of a prealloyed manganese, sulfur, ferrous based powder, copperand carbon wherein the mixture has a copper content higher than 2% byweight.
 2. A powder according to claim 1 comprising: Component WeightPercent copper (Cu) 2.0 to 5.0 carbon (C) 0.2 to 1.0 prealloyed Mn Sferrous based powder balance.


3. A powder according to claim 1 comprising: Component Weight Percent Cu2.5 to 4.5 C 0.2 to 0.7 prealloyed Mn S ferrous based powder balance.


4. A powder according to claim 1 comprising: Component Weight Percent Cu3.0 to 4.0 C 0.4 to 0.7 Prealloyed Mn S ferrous based powder balance.


5. A forged article produced from the powder mixture of claim
 1. 6. Aforged connecting rod produced from the powder mixture of claim 1.